This topic from molecular biology in which explain about genetic material of eukaryotic and prokaryotic genomes.

1. GENE AND GENOME
Submitted To: Submitted By:
Mrs. Mukesh Jangra Amit
B. Sc. (Biotech)
(2991710035)

2. Introduction
 Gene is unit of heredity which is transferred from a parent to
offspring.
 Term gene coined by Johanson in 1909.
 Gene theory proposed by T. H. Morgan.
 First Mendel used the term “Factor” for gene which is hereditary
unit.
 Suton and Boveri suggest that gene are present on chromosome.
 The gene are arranged on the chromosome in the linear order and
that region on which gene present is called locus.

3. Number of Genes on a Single Chromosome
 Total number of genes on a single chromosome is different in different organisms.
 Bacteriophage virus R17 consists of only three genes, SV40 consists of 5-10
genes.
 E. coli bacteria have more than 3000 genes on single 1 mm long chromosome.and
each chromosome in human contains hundreds to thousands of genes.

4.  Genes are Separated into exons (protein-coding) and introns (non-protein
coding)
 Average number of exons per gene ~ 10 (1-363)
 Average length of a gene ~ 54,000bp (200-24,000,000bp)
 Average exon size ~ 288bp (10-180bp)
 Intron size range ~ 30-11,000,000bp

7. Types of Gene
On the basis of their behavior, the genes may be classified into the following types:
1. Basic genes: These are the fundamental genes that bring about expression of
particular character.
2. Lethal genes: These bring about the death their possessor.
3. Multiple genes: When two or more pairs of independent genes act together to
produce a single phenotypic trait.

8. 4. Cumulative genes: Some genes have additive effects on the action of other
genes. These are called cumulative genes.
5. Pleiotropic genes: The genes which produce changes in more than one
character is called pleiotropic gene.
6. Modifying genes: The gene which cannot produce a character by it self but
interacts with other to produce a modified effect is called modified gene.
7. Inhibitory genes: The gene which suppresses or inhibits the expression of
another gene is called inhibitory gene.

9. Gene Action
One gene–one enzyme hypothesis
 The idea that genes act through the production of enzymes, with each gene
responsible for producing a single enzyme that in turn affects a single step in
a metabolic pathway.
 The concept was proposed by George Beadle and Edward Tatum.
 He took genetic mutations in the mold Neurospora crassa, and subsequently
was dubbed the "one gene–one enzyme hypothesis"
 Some genes are encode protein that are not enzyme. Enzyme are just category
of protein.
 Some genes encode a subunit of protein ,not whole protein.

10. One gene–one polypeptide
 One gene one enzyme hypothesis was modified by Vernon Ingram in 1962.
 The theory that each gene is responsible for the synthesis of a single
polypeptide.
 It was originally stated as the one gene-one enzyme hypothesis by the US
geneticist George Beadle in 1945 but later modified when it was realized that
genes also encoded non enzyme proteins and individual polypeptide chains.
 It is now known that some genes code for various types of RNA involved in
protein synthesis.

11. Gene in Protein Synthesis
To explain the mechanism of gene action in protein synthesis is regulated by
three specific genes located on chromosomes.
1. Structural genes: It regulates to produce specific m-RNA and determine
the kind of protein to be synthesized.
2. Operator genes: These genes act as switches to turn on or turn off the
activities of structural genes, regulating the elongation and termination of
polypeptide chain.
3. Rugulator genes: These genes produce certain protienaceous substance
called repressors which prevent the operator genes from their action.

12. Gene in Protein Synthesis

13. Genome
 A Genome is an organism’s complete set of DNA, including all its genes.
 Genome is the complete set of genetic information in an organism.
Types of genome:
1. Viral genome
2. Prokaryotic genome
3. Eukaryotic genome

15.  Viruses have genes that encode a minimum of two proteins:
i. Replicase- an enzyme that replicates the genome.
ii. Capsid- a protein that protects genome.
 Viruses may have genes that encode for proteins that help in infection.
i. Glycoprotein- (enveloped viruses only) allows virus to enter a cell, targets
specific cell types for virus, and aids in virus assembly.
ii. Host shutoff proteins- virus proteins that shutoff host activities so only virus
genes get made.
iii. Anti-host defense proteins- These proteins prevent the host defense
mechanism from stopping virus replicator.

16. Prokaryotic Genome
 Prokraytic genome are two type bacteria and archaea.
 The size of prokaryotic genome about 1 million to 10 million base pair of DNA.
 The size of Bacterial chromosomes ranges from 0.6 Mbp to 10Mbp.
 The size of Archael chromosomes ranges from 0.5Mbp to 5.8Mbp.
 The size of prokaryotic genome is directly related to their metabolic capabilities-
more gene means more protein and enzymes make.
 The maximum part of prokaryotic DNA is working.
 The smallest Archae genome is from Nanoarchaeum equtans (491kbp).
 The smallest Bacterial genome is from mycoplasma genitalium (580kbp).
 The smallest free-living organisms have a genome size over 1Mbp.

18. Eukaryotic Genomes
 Eukaryotic genomes are composed of one or more linear DNA
chromosomes. Gametes, such as ova, sperm, spores, and pollen, are
haploid, meaning they carry only one copy of each chromosome.
 Eukaryotic genome size are variable in taxonomic group that is why called
C-paradox.
 The C value paradox is that the amount of DNA in a haploid genome (the
1C value) does not seem to correspond strongly to the complexity of an
organism.
 There is two type of genome in eukaryotic cells-
i. Nuclear genome
ii. Organelle genome

20. i. Nuclear Genome
 It is the major part of eukaryotic DNA in which 85% of which junk and only
15% of DNA is in working.
 Nuclear genome includes-introns, exons, jumping gene or transposons.
 The nuclear genome refers to the DNA in the chromosomes contained in the
nucleus; in the case of humans the DNA in the 46 chromosomes.
 It is the nuclear genome that defines a multicellular organism; it will be the
same for all cells of the organism.

21. ii. Organelle Genome
Organelle Genome are two types-
1. Mitochondrial DNA
2. Plastid DNA

22. Mitochondrial DNA
 Mitochondrial DNA (mt DNA or m DNA) is the DNA located in mitochondria,
cellular organelles within eukaryotic cells that convert chemical energy from food
into a form that cells can use, adenosine triphosphate (ATP)
 Mitochondrial DNA contains 37 genes, all of which are essential for normal
mitochondrial function.
 Thirteen of these genes provide instructions for making enzymes involved in
oxidative phosphorylation.

23. Plastids DNA
 Plastids are the site of manufacture and storage of important chemical
compounds used by the cells of eukaryotes.
 They often contain pigments used in photosynthesis, and the types of
pigments in a plastid determine the cell's color.
 Plastids that contain chlorophyll can carry out photosynthesis and are
called chloroplasts.
 Plastids can also store products like starch.

24.  In plants, plastids may differentiate into several forms, depending upon which
function they play in the cell.
 Chloroplasts: Green plastids for photosynthesis; see also etioplasts, the
predecessors of chloroplasts
 Chromoplasts: Coloured plastids for pigment synthesis and storage
 Elaioplasts: For storing fat.